With the rapidly growing interest in wireless communications and Internet connectivity, wireless service providers are competing to capture the market share by offering their customers access to applications that take advantage of both technologies.
In a mobile Internet Protocol network, a mobile communication device (a mobile node), such as a mobile host or router that changes its point of attachment from one network to another, communicates with a target host on an Internet Protocol (“IP”) network by means of two devices, a “foreign agent” and a “home agent.” Typically, the foreign agent's functionality is incorporated into a router on a mobile node's visited network. The foreign agent provides routing services for the mobile node while it is registered with the home agent. For example, the foreign agent de-tunnels and delivers data packets that were tunneled by the mobile node's home agent to the mobile node.
A home agent is typically incorporated into a router on a mobile node's home network. The home agent maintains current location information for the mobile node. When one or more home agents are handling calls for multiple mobile nodes simultaneously, the home agents are providing, in essence, a service analogous to a virtual private network service.
Mobile Internet Protocol requires the link layer connectivity between a mobile node (a mobile entity) and a foreign agent. However, in some systems the link layer from the mobile node may terminate at a point distant from the foreign agent. Such networks are commonly referred to as third-generation (3G) wireless networks. A 3G network delivers much greater network capacity than many currently existing circuit-switched digital mobile networks. The increased availability of bandwidth in 3G networks opens up a new generation of applications to wireless subscribers such as collaborative and multimedia services.
One of the goals of the architecture of next generation IP networks is a framework for the introduction of new multimedia services and features at the Internet speed, using IP-based applications and protocols. This has led to a differentiation of the functional and operational aspects of multimedia networks within three layers or planes, defined broadly as media processing, control and service creation. The service creation plane is sometimes further subdivided into an application plane and a data plane. The initial next generation IP networks have been aimed at building the infrastructure that realizes the architectural framework. At the same time, the list of IP-based multimedia services ready for deployment has grown steadily ahead of what may eventually be a great multiplicity of new services and features. Thus, the successful introduction of the next-generation services depends not only on how useful the services are to end users, but also on how intelligently they integrate capabilities of the underlying network system.
Many next-generation services, such as an instant messaging service, require that a user knows the state of other users with respect to connectivity and availability and their willingness to communicate, i.e., presence information, that is provided by a presence service. A presence service is the implementation of the methods and protocols to realize the practical use of network presence in real services, which require presence-related information. An example of a presence-based service is an instant text messaging service, where one user may detect the presence of another user and then send an immediate text message to that user.